The invention relates to pressure regulators and particularly to pressure regulators for supplying water to irrigation sprinklers and nozzles.
Irrigation systems often have several sprinklers and nozzles arranged along an extended water supply pipe. For example, a water supply pipe in a center pivot irrigation system may extend a quarter to half a mile (400 to 800 meters). The water supply pipe may have a diameter of six to ten inches (152 to 254 millimeters) and provide water for over a hundred sprinklers arranged along the pipe. Each sprinkler is typically connected to the water supply pipe by a smaller water pipe that extends vertically and includes a pressure regulator.
The sprinklers are typically designed to receive water under a relatively low pressure and within a narrow pressure range. Pressure regulators reduce the pressure in the water supply pipe to a pressure suitable for a sprinkler or nozzle. The pressure regulator ensures that the water pressure is within the design range of the sprinkler or nozzle.
The elevation of the water supply pipe in an irrigation system rises and falls as the pipe travels over the hills and low points of an agricultural field. These changes in elevation vary the pressure in the water supply pipe. The pressure regulators adjust to the changes in pressure such that water flows to the sprinklers and nozzles at a relatively uniform pressure.
Nelson Irrigation Corporation of Walla Walla, Wash., U.S.A., manufactures and sells flow-through type pressure regulators having a tubular housing with an inlet at one end and an outlet at the other end. Pressure loss through the regulator is controlled by a gap between a valve seat and a tubular plunger in the regulator. The tubular plunger is biased away from the valve seat in a normally open condition by a compression spring. The pressure of the flow at the outlet of the regulator acts on a diaphragm in the regulator. The diaphragm is attached to and moves with the plunger.
Within a normal operating flow rate range, the spring force balances against the outlet pressure applied to the diaphragm. This balance sets the opening between the valve seat and the plunger to cause the desired pressure loss at the flow rate demanded by the sprinkler. An increase in the inlet pressure will initially increase the pressure at the outlet and thus increase the pressure on the diaphragm. Due to the pressure increase, the diaphragm moves the tubular plunger towards the valve seat to narrow the gap and reduce the pressure at the outlet of the regulator. The counteracting forces of the spring and the outlet flow pressure move the plunger and adjust the gap to achieve a substantially uniform outlet pressure of the flow leaving the pressure regulator.
The valve seat and a strut(s) supporting the valve seat tend to collect debris from the water flow. Water for the sprinklers is often drawn from ponds and irrigation ditches near agricultural fields. The water is dirty with suspended grasses, other plant material and other debris. The grass and other fibrous debris can wrap around and collect on the valve seat and its support strut(s). Debris collecting on the valve seat and strut obstructs the flow through the regulation gap and can interfere with the movement of the plunger. The debris can impair the operation of the pressure regulator, causing the pressure of the output flow to vary from the desired output pressure, reducing the rate of flow through the pressure regulator, and causing excessive pressure losses through the regulator.
Efforts to prevent debris from collecting on the valve seat and strut include having a cantilever-beam type single strut which is less likely to collect debris than multiple struts. See U.S. Pat. Nos. 7,048,001 and 7,140,595 and U.S. Patent Publication 2012/0285561. While a single strut has been successful in suppressing the collection of debris on the strut and valve seat, there remains a continuing problem of debris collecting on or near the strut and valve seat in a pressure regulator.
A pressure regulator having an adjustable valve seat is shown in U.S. Pat. No. 7,401,622, wherein the valve seat is substantially offset from the flow passage so that the valve seat may function as an On-Off valve. Shifting the seat to such an extent resulted in extreme turns in the water passage near the valve seat and inlet to the plunger. The extreme turns tend to cause excessive pressure losses and nonuniform flow at the outlet. Thus, there is a continuing need to reduce pressure losses in pressure regulators and for the regulators to discharge water in a flow that has a relatively uniform velocity profile.